Re: Array searching, grep, first

I'll agree that it would probably be more efficient to create a hash and work with that, however here is a way to get the array index using grep

#!c:\perl\bin\perl.exe -w

use strict;

my @csvlist = qw(file3 file6 file1 file10 file5 file2 file7 file4 file
+9 file8);
my @listofnames = qw(file1 file2 file3 file4 file5);

for my $x(@listofnames)
{
    my ($test) = grep { $csvlist[$_] =~ /$x/} 0..$#csvlist;
    print "$x found at index: $test\n";
}
[download]

That is, if I understood your question correctly.

Update
Here is the output from the test script above:

file1 found at index: 2
file2 found at index: 5
file3 found at index: 0
file4 found at index: 7
file5 found at index: 4
[download]

Update: diotalevi makes a good point below about the inefficient use of grep that I displayed above.

Comment on Re: Array searching, grep, first Select or Download Code

Replies are listed 'Best First'.
Re^2: Array searching, grep, first by diotalevi (Canon) on Sep 01, 2005 at 19:02 UTC
If you're going to use grep that way, you're doing unnecessary work. Either rewrite that grep as a for loop or use List::Util::first. `my $index; for ( 0 .. $#csvlist ) { if ( $csvlist[$_] =~ /$x/ ) { $index = $_; last; } } use List::Util 'first'; my $index = first { $csvlist[$_] =~ /$x/ } 0 .. $#csvlist` [download]	[reply] [d/l]
Re^3: Array searching, grep, first by ChrisR (Hermit) on Sep 01, 2005 at 19:07 UTC
You are quite right. `grep` will search through the entire list on every iteration. `first` is the way to go but your looping through the indexes is more self explanatory.	[reply] [d/l] [select]
Re^2: Array searching, grep, first by jimbus (Friar) on Sep 01, 2005 at 18:13 UTC
There are usually 90-120 lines in the CSV per day, so I'm not sure it matters. Can I get a little explaination on whats going on with `grep { $csvlist[$_] =~ /$x/} 0..$#csvlist;` it looks like it would be useful. Jimbus Never moon a werewolf!	[reply] [d/l]
Re^3: Array searching, grep, first by friedo (Prior) on Sep 01, 2005 at 18:29 UTC
What's going on here is that the list that is being `grep`ed consists of the numbers `0..$#csvlist`. (Or zero through the highest index in the array.) The conditional inside the grep block looks at the array item indexed at each number and returns that number if the condition is true.	[reply] [d/l] [select]


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